12v 5v power supply

[cd520]

You can find really cheap PC power supplies with nice current ratings. I have one I converted over and use it for the 12V side on a 20A device and it works great. You cant buy a stand alone 12V 25A supply for anything close to the price of a cheap PC supply. I imagine they recommend such a higher wattage resistor because the fact most people use these things for long periods of time and obviously a higher rated resistor will last longer against the heat. I cant remember what resistor/resistor combo I'm using but 20W comes to mind and even it gets toasty.

 

[Cyparagon]

The power rating of a resistor is the power it can withstand indefinitely. If a resistor is rated for 1/4W, you can run it at 1/4W. Resistors can run hotter than silicon devices and heat has less impact on lifespan.

 

[Ignis Fatuus]

It's always worked fine for me, and has never shut off the PC.

Thats because its under a load.

Some PSUs are 'switching' units, which means you need to keep a load on it to keep it going. Older ones are usually not, so you wouldn't need a load.